Abbas - Tanwîr al-Miqbâs min Tafsîr Ibn ‘Abbâs
(These are they who purchase error at the price of guidance), they chose disbelief instead of faith and exchanged guidance with error, (so their commerce did not prosper), they did not prosper in their bargain but on the contrary (neither were they guided) to overcome their error.
Those are they who have bought error for guidance, that is, they have exchanged the latter for the former; so their commerce has not profited them, that is to say, they have gained nothing from it, indeed, they have lost, because their destination is the Fire, made everlasting for them; nor are they guided, in what they did.
Those are they who have bought in exchange for guidance error, that is, darkness and being veiled from the path of truth, namely, religion, or from the truth [itself], for error is dispersed in the face of guidance through the original light of preparedness; so their commerce brings no profit [for them], because their capital derives from the world of light and subsistence so that they might acquire by this [capital] what resembles it in the way of effusive, perfecting light through the sciences, deeds, wisdoms, gnosis, character traits and virtuous dispositions becoming thereby rich in reality, deserving of proximity, dignity, exaltation and esteem before God, but they have not profited by acquiring [all of] that; [nor are they guided] and thus the original guidance that had been their commodity and capital is lost by the disappearance of their preparedness and the sullying of their hearts by the rust that necessarily leads to eternal veiling and deprivation and so their loss is an eternal one without beginning or end.
(These are they who have purchased error with guidance) saying it means, "They pursued misguidance and abandoned guidance. '' Mujahid said, "They believed and then disbelieved,'' while Qatadah said, "They preferred deviation to guidance.'' Qatadah's statement is similar in meaning to Allah's statement about Thamud,
(And as for Thamud, We granted them guidance, but they preferred blindness to guidance) (41:17).
In summary, the statements that we have mentioned from the scholars of Tafsir indicate that the hypocrites deviate from the true guidance and prefer misguidance, substituting wickedness in place of righteousness. This meaning explains Allah's statement,
(These are they who have purchased error with guidance), meaning, they exchanged guidance to buy misguidance. This meaning includes those who first believed, then later disbelieved, whom Allah described,
(So their commerce was profitless. And they were not guided), meaning their trade did not succeed nor were they righteous or rightly guided throughout all this. In addition, Ibn Jarir narrated that Qatadah commented on the Ayah,
(So their commerce was profitless. And they were not guided), "By Allah! I have seen them leaving guidance for deviation, leaving the Jama`ah (the community of the believers) for the sects, leaving safety for fear, and the Sunnah for innovation.'' Ibn Abi Hatim also reported other similar statements.
Maududi - Sayyid Abul Ala Maududi - Tafhim al-Qur'an
They deceive themselves by imagining that their duplicity will safeguard their interests but obviously their policy will prove harmful in this world as well as in the next. A hypocrite might succeed in deceiving some people for some time but he cannot deceive all people for all times. When such a person is exposed, he loses all honour once and for all. As to the Hereafter, mere lip-service will carry no weight there because it is deeds alone that matter there.
"A disease": the disease of hypocrisy; and "Allah is increasing their disease all the more" means that He does not punish the hypocrites for their hypocrisy immediately, but gives them respite so that when their duplicity appears to succeed apparently they become more and more convinced of its efficiency and they go on becoming more and more hypocritical in their attitude and conduct.
That is,"Just as the other people of your nation have accepted Islam truly and sincerely, so should you also accept it truly and honestly, if you profess to accept it".
They regarded as tools the people who had accepted Islam sincerely and exposed themselves to troubles, hardships and dangers. In their opinion it was nothing but folly to earn the hostility of the whole country merely for the sake of truth and righteousness. They considered it wisdom not to bother about the right and the wrong at all but to look only after one's own interests.
Shayatin plural of Shaitan, is an insurgent, haughty and devilish person, or an evil genius. This word is used both for the men and the jinn. Though it has mostly been used in the Qur'an for the jinn devils, in some places it has also been applied to human devils, and from the context it can easily be judged where it refers to human and where to jinn devils. Here it refers to the Arab chiefs who were in the fore-front in their opposition to Islam.
Those are they who have bought error for guidance; so their commerce has not profited them; nor are they guided. This alludes to those who have neglected what is due ḥuqūq by remaining in the familiar territories of worldly fortunes ḥuẓūẓ. [They] have lost their bargain so their commerce has not profited them. Those who are content with this world over the next are in manifest loss. Those who prefer this world or the next over the Real have the most intense loss. Although the one who suffers the loss of [the gardens] of bliss will come up short the one who is afflicted with distance from intimate conversation and the disengagement of his heart from his Protector the one who remains in the captivity of carnal desires with no messenger [reaching] his heart the one without attainment for his spirit without intimate conversation with Him without approach to Him without the witnessing [of Him] in his innermost self-this is the one who [truly] suffers and is afflicted. If even a moment slips away his Lord has slipped away. Moments have no substitutes or alternates. Thus someone said: You were the pupil of my eye. [The organ] by which I see wept for you. Anyone who has a will after you let him die for I used to be a guard over you.